Non-impregnated fleeces have excellent properties with respect to puncture proofness and resistance to further tearing. Their main drawback resides, however, in that their surface is unsteady and is very strongly changed in particular when being stretched. A further drawback of these fleeces resides in their strongly varying thickness. If such fleeces are used as a carrier material for a coating of synthetic plastics material it is, for the purpose of compensating variations in thickness and for the purpose to eliminate the unsteadiness of the surface of the fleece, necessary to provide correspondingly thick and heavy and thus expensive coatings of synthetic plastics material. It has, however, been proposed to use as the coating material foamed PVC or foamed PUR, so that the weight becomes reduced, but such foamed coatings have an only low abrasion resistance and tend to splitting.
It is also known to produce the coating from an aqueous dispersion of synthetic plastics material containing either hollow microspheres or compact particles from which are formed hollow microspheres when supplying heat during solidification of the dispersion of synthetic plastics material. These hollow microspheres are closed cells, so that the coating shows a closed-cell foam structure. The mentioned drawbacks can only partially be avoided also with such a coating, because this coating must have a corresponding thickness. The closed-cell foam structure is, furthermore, not permeable for water vapour.
It is further known to make a substrate by incorporating a synthetic plastics material into a fleece. Thus it has already been proposed to introduce into a fleece a polymer solution formed of solvents miscible with water and of polyurethane and to allow to coagulate this solution, the liquid polymer solution becoming solidified during coagulation. Subsequently, the solvent is removed by washing with water, whereby open-cell pores are formed. Such a procedure is circumstantial. Furthermore, the solvents used are toxic and harmful to the environments. A further drawback resides in that only thermoplastic synthetic plastics material can be used for such a procedure and in that such synthetic plastics materials give rise to problems because they tend to smearing on grinding.
There has also already been proposed a process for producing porous flat shaped articles of textile having a leather-like grain, according to which process a base fabric of shrinkable fibres is impregnated at one side or at both sides with a flowable and heat-reactive polymer having, for example, been given a foam-like condition by introducing air, whereupon the impregnated fabric is allowed to dry by supplying heat and is allowed to shrink by a treatment with water or steam (DE-A-No. 21 64 852). There results an absorbent flat shaped article having a leather-like grain and which can be used as a dish rinsing cloth, scrubbing cloth, wiping cloth on the like. In this case it is a premise to use a fabric of natural fibres which shrink during washing, so that there results a leather-like grain but no oile effect. If this known flat shaped article is stretched or extanded, there results, on account of the utilization of the fabric, equally an unsteady, uneven sight surface. The use of this fabric makes difficult the production of exact cut edges because the fabric tends to fraying.
It is also known to impregnate a carrier body formed of a fabric, knitting or fleece with a synthetic plastics material having properties of an elastomer or similar to that of an elastomer and having embedded therein hollow microspheres, noting that the surfaces of the substrate thus produced have been worked by grinding operation or the like and thus show partially opened hollow microspheres (DE-C2-No. 31 17 721). There results a pile effect at the surface of the substrate now having a low density on account of the embedded hollow microspheres and having also a plane surface, but the substrate thus formed is not or scarcely permeable for water vapour and is also relatively stiff. The tearing resistance, the stitching resistance and the humidity absorption are equally unsatisfactory and the application of a coating is not possible.
In general, it is difficult to correctly predetermine the amount of synthetic plastics material, which amount is mainly dependent on the content in solid matter of a solution or dispersion, to be introduced into a fleece, which is subsequently ground, for obtaininq a nubuk or pile effect. A high content of the solution or dispersion in solid matter results in a hard, stiff product of low porosity and thus of negligible absorbency and of poor tearing resistance and stitching resistance, while a low content in solid matter has as an effect that the synthetic plastics material is mainly accumulated at the crossing points of the fibres, in consequence of which the tearing resistance and the stitching resistance is equally poor and the material becomes cornered on bending and can be ground only with great difficulties. A further disadvantage is the low abrasion resistance of the material and the high energy requirement for evaporating the water or the solvent.
The term "impregnate" is, in the present case, to comprise not only immersion of the textile material into a bath but also each other method for applying a liquid onto the textile material.